The invention relates to a supporting system for a helical or ring-bar delay line of a travelling wave tube wherein the delay line is supported by a number of dielectric support rods which are arranged parallel to one another along generating lines of the line, and wherein a number of clamping rings which consist of resilient material and press the support rods against the delay line are provided.
Travelling wave tubes with helical delay lines are generally known from U.S. Pat. Nos. 3,506,872; 3,863,092; and 3,678,326, all incorporated herein by reference.
German Pat. No. 1 110 328, incorporated herein by reference, discloses a supporting system for the helical delay line of a travelling wave tube wherein the helix is held by and between three insulating rods which are arranged parallel to the helix axis and wherein at least one unslotted metal ring which presses the insulating rods against the helix is provided. In this system, the inside diameter of the thin-walled metal ring is somewhat smaller than the diameter of the periphery of the helix supporting system and the metal ring consists of a material which is designed so that it is elastically resilient in a radial direction. With the aid of this system it is achieved that only centrally aligned, defined balance forces are exerted on the helix supporting system.
In many travelling wave tubes, a system which consists of, for example, three ceramic (quartz) rods and a plurality of resilient clamping rings which consist of metal and serve to hold together the system, is used for supporting the helical delay line.
The higher the operating frequency of the travelling wave tube the smaller has to be the overall diameter of the tube. Thus the metallic clamping rings come closer and closer to the helical delay line. The clamping rings are then arranged in the high-frequency field of the delay line and therefore produce reflections which are more or less strong and undesired because they lead to resonance effects.